1. Field of the Invention
The invention relates to a cooling channel cover for a one-piece piston of an internal combustion engine, the piston having a closed cooling channel that runs around inside the piston crown, at the level of the piston ring band, and a ring-shaped recess provided between the piston ring band and the piston shaft. The piston shaft is connected with the piston crown via hubs suspended on the piston crown.
2. The Prior Art
A multi-part cooled piston having a cooling channel arranged in the edge region of the piston head is described in German Publication No. DE 40 39 751 A1, which channel is covered with a sheet-metal ring essentially structured like a cup spring. This sheet-metal ring is structured in one piece and can be easily assembled with the piston only because the piston is structured in two parts. In this connection, it is necessary to assemble the sheet-metal ring with the upper piston part first, before the upper piston part is connected with the lower piston part.
Furthermore, pistons are described in German Publication No. DD 252 638 A1 and German Publication No. DE 41 34 530 A1, in which a wall part that covers the cooling channel that is open to the bottom, and runs around the circumference in ring shape, is structured as an open sheet-metal ring, which rests in a groove against the inside circumference of the piston ring zone, and against the outside circumference of the combustion chamber wall, respectively, taking advantage of its plastic deformation according to the Seeger ring principle, i.e. biased in the radial direction.
Furthermore, a multi-part piston having a cooling channel described in German Patent No. DE 42 08 037 C2, in which the cooling channel, which is open to the bottom, is covered by a biased cup spring, which is divided into at least two parts on its circumference, and rests freely on supports against axially opposite sides, radially on the inside and the outside.
Finally, one-piece cooling channel pistons having a cooling channel arranged in the edge region of the piston head are known from European Patents Nos. EP 0 561 871 B1 and EP 0 799 373 B1. In these patents, the channel is also closed off with cover rings structured like cup springs, or cover rings structured like cup springs and provided with a collar.
A disadvantage of the aforementioned embodiments is that the cover ring or cup spring must be structured in two parts, in order to be able to be assembled. Furthermore, during assembly, each of the two semi-circular ring halves must be individually introduced into corresponding bearings on the piston crown, in the biased state.
Proceeding from this, the invention is based on the task of creating a cooling channel cover for a one-piece piston of an internal combustion engine, which cover can be installed easily and quickly, and allowing for a reduction in piston weight as compared with the known state of the art.
This object is accomplished by means of a one-piece plastic or spring steel ring, U-shaped in cross-section, which has a ring bottom and an outer shank around the circumference, molded onto the ring bottom and angled off radially to the outside, and an inner shank around the circumference, angled off radially to the inside. A first film hinge radially deflects the ring shank of the ring formed by the hinge, in its positional plane. The ring has a first radial division having a mouth width and a second radial division, opposite the first division; on the circumference, which does not separate the radially angled outer shank that runs around the circumference, to form the first film hinge. In this manner, the cooling channel cover allows very simple and quick assembly on the piston, and the plastic/spring stell construction allows for a reduction in the piston weight. Furthermore, the plastic ring has a second film hinge, by means of which at least one radial deflection of at least one of the radially angled shanks is permitted, so that in order to close off the cooling channel, the shanks engage in a conical stepped recess on the inner circumference of the cooling channel.
The first film hinge is preferably determined by a material thickness of the outer shank. In a preferred embodiment, the second film hinge is formed on the outer shank or inner shank, and the film hinges are formed by a material weakening at an angle of the outer and inner shanks from the ring bottom.
The outer shank is angled off radially to the outside relative to a crosswise piston axis, and the inner shank is angled off radially to the inside, relative to the axis.
In a preferred embodiment, slits that extend close to the ring bottom are made in the outer and inner shanks, with the slits being non-uniformly distributed over the circumference of the ring, in order to produce different ridge lengths. The first film hinge is preferably arranged in a region between the slits. The slits preferably have a width of 2 to 3 mm and the ridge lengths between the slits are 15 to 20 mm.